Kennedy — Large Ions and Condensation- Nuclei from Flames. 63 



mercury move to and fro in A without splashing, the filtered air is thoroughly 

 mixed with that containing the nuclei, and the dilution is such that the nuclei 

 have only -^ig-th of their original concentration. By repeating the process a 

 dilution of 4-^-5- is obtained, and, similarly, any intermediate amount of dihition 

 may be produced. When the suitable concentration has been obtained, the 

 vessel A is put in communication with the Aitken apparatus, and a portion 

 of the air in it is passed through the apparatus so as to drive out the air 

 in the intervening tubes. In this way all the space joining the counting 

 apparatus to the vessel A is filled with air at the required concentration, and 

 the test is made as described in Aitken's paper. About ten tests were made 

 of each sample of air, and the mean of these results taken to calculate the 

 number of nuclei per c.c, correction being made for the variation in the 

 pressure in A by the introduction into the counter of the amounts of air 

 necessary for the tests. 



Disappearance of the Nuclei. 



Investigation was first made on the nature of the disappearance of 

 uncharged nuclei, and for this purpose the gasometer was filled rapidly with 

 flame-gas as indicated in fig. 1, but in this case the flame-gas immediately 

 after leaving the flame was subjected to a very strong electric field to remove 

 all the ions. The gasometer then contained great numbers of uncharged 

 nuclei, but tests made with the electrometer showed that the number of 

 ions present was too small to be measured. Measurements of the number 

 of nuclei per c.c. were made at intervals, and Table II contains such a series 

 of measurements, n being the number of nuclei per c.c. 



Table II. 



Time (minutes) 



H X 10-3 



n-i X 10' 







1125 



8-9 



25 



30G 



32-7 



65 



164 



61 



95 



108 



92-5 



